1. Field of the Invention
The present invention relates to a route guiding apparatus, and particularly to a device employing a route search using public transportation routes in addition to vehicular routes.
2. Description of the Background Art
A navigation apparatus including map data, which searches for a route to a destination and presents the route to a user, is conventionally known. A significant technical object of such a navigation apparatus is to provide the user with a route that allows the user to reach a target destination in a short time.
One guiding technique is disclosed in Japanese Patent Laid-Open Publication No. Hei 7-55484. According to this technique, a user designates a destination, and then inputs a target arrival time. The apparatus computes an estimated arrival time at the destination taking into account information such as traffic condition information, and compares the target arrival time and the estimated arrival time. When the estimated arrival time is later than the target arrival time, information on an alternative transportation, such as rail lines, is provided to the user. Specifically, the apparatus informs the user that xe2x80x9cAs is, it is impossible to reach by the target arrival timexe2x80x9d, and displays the rail option, the telephone number of the destination facility, and other such information. When the user selects the rail option, the time required to travel from the current location to a nearby station, and from a station near the destination to the destination, is calculated. Information such as the name of the transportation service, the departure station, the arrival station, and the transfer station are also offered.
According to the above technique, a route using alternative transportation, specifically, public transportation, is searched for when the estimated arrival time is later than the target arrival time. Such a method is disadvantageous in that the efficacy of the use of public transportation is not necessarily ensured. In the above conventional technique, it is further described that a ratio between the travel time required by driving a vehicle and the travel time required by public transportation is compared to a predetermined value, and, when the ratio is less than the predetermined value, guiding information concerning public transportation is not offered. However, it is difficult to determine which traveling means is more appropriate based only on the required travel time because other factors are concerned. For example, ticket fees are additionally necessary when using railway.
An object of the present invention is to provide an apparatus which offers a route using public transportation when the advantage of using public transportation is ensured, thereby achieving enhanced user convenience and increased reliability of navigation systems.
Another object of the present invention is to conduct a search for a route using public transportation by employing the same search algorithm used for vehicular route searches, and to thereby provide an apparatus having a simplified configuration.
A further object of the present invention is to provide an apparatus which can precisely indicate the current location to the user when offering a route involving public transportation.
A still further object of the present invention is to provide an apparatus which can safely guide the user when offering a route using public transportation.
To accomplish the above objects, a route guiding apparatus of the present invention comprises a calculation means for calculating a cost associated with a route using public transportation (also referred to as a public transportation route) and a cost associated with a vehicle only route (also referred to as a vehicular route), and a control means for indicating the route using public transportation when the cost of the route using public transportation is less than vehicle only route adjusted by a predetermined factor. The route using public transportation (public transportation route) is a route including, in at least one portion of the route, a service route of a public transportation service such as railway, subway, bus, ferry, and airplane, and may also include traveling on foot. The vehicle only route (vehicular route) is a route including no public transportation service route, and which therefore may be traveled by motor vehicle only. By comparing the public transportation route and the vehicular route using the associated costs, and indicating the public transportation route when the economy of the public transportation route exceeds a predetermined value, the public transportation route is offered when there actually exists a merit in its use. A cost of a route referred to herein comprises not only monetary costs, but includes weighted factors related to distance, time, and fees, which must be incurred when traveling from the current location to the destination. When a route involves greater distance, time, or fees, the cost of the route is increased. By reflecting the loads related to distance, time, and fees in the cost, a comprehensive comparison of a public transportation route and a route using vehicle only can be accomplished. The financial factor can be eliminated from the cost calculation when financial expenses are not relevant to the user.
In one aspect of the present invention, the distance load is converted into a time load, and the cost of the public transportation route and the cost of the vehicular route are compared in units of time. In conventional techniques, a vehicular route cost is calculated in units of distance based on the link cost (sum of the cost allotted to each link when the road data is configured using links and nodes) or node cost (sum of the cost allotted to each node when the road data is configured using links and nodes) designated according to distance and road type, and the route having the smallest cost is determined as the optimal route (when traffic is congested, the cost factor of the congested link is increased). However, as a public transportation service generally operates according to a predetermined service schedule or timetable, it is more appropriate to evaluate a public transportation route in units of time rather than in units of distance of the service route. Accordingly, a vehicular route is also calculated in units of time rather than distance, to facilitate judging which of the public transportation route or the vehicular route is more appropriate. To calculate the cost of the vehicular route in units of time in the present invention, the distance cost used in conventional route search techniques is divided by the vehicle velocity. The vehicle velocity is preferably a value in accordance with the road type, and may be the legal speed limit on the road or a statistically calculated average velocity.
According to another aspect of the present invention, the calculation means calculates, for the vehicular route, the estimated arrival time via a static route and the estimated arrival time via a dynamic route. When the estimated arrival time via the dynamic route exceeds the estimated arrival time via the static route by a predetermined time interval, the control means indicates the public transportation route. Vehicular routes may be classified into one of two types, a static route obtained based on the connection relationship in map data without considering the current traffic condition, or a dynamic route generated based on the connection relationship in map data while also considering traffic information that continually changes over time. When the estimated arrival time from the current location to the destination via the dynamic route exceeds the estimated arrival time from the current location to the destination via the static route by a predetermined interval, the road most likely cannot be smoothly traveled due to traffic congestion or other reasons. Accordingly, in such a case, the public transportation route is indicated. In this way, the public transportation route can be offered to the user when there exists additional merit in its use. The dynamic route can be indicated as the recommended route when the cost of the dynamic route is smaller than the cost of the public transportation route.
In a further aspect of the present invention, the route guiding apparatus further comprises a memory means for storing in advance a zone in which public transportation can be used, and the control means offers a route using public transportation when the current location and/or the destination is located within the zone in which public transportation can be used.
In a still further aspect of the present invention, a public transportation route is offered when there exists a plurality of public transportation services that can be used. When there is only one usable public transportation service to reach the destination, the certainty of arriving at the destination is determined to be lower than a case when a plurality of such public transportation services exist. Accordingly, the user can be reliably guided to the destination by indicating a public transportation route when there exists a plurality of public transportation services that can be used.
In another aspect of the present invention, the route guiding apparatus includes a detachable portable terminal device. The portable terminal device stores the guiding information for a public transportation route. The device guides the user to the destination based on the stored route guiding information when the user detaches and carries the portable terminal device to use public transportation.
In a further aspect of the present invention, the portable terminal device is prohibited from being detached during vehicle traveling. In addition, when the user dismounts from the vehicle, the route guiding apparatus urges the user to detach and carry the portable terminal device.
According to a still further aspect of the present invention, for the purpose of conducting an efficient search for a public transportation route, the route guiding apparatus comprises a memory means for storing map data related to public transportation routes as link information and node information, and the calculation means calculates the cost of a public transportation route based on such link information and node information. The public transportation service routes are configured using links and nodes which are similar to the links and nodes constituting the vehicular routes, allowing the road data and the public transportation data to be treated seamlessly. With this arrangement, a public transportation route can be searched for by employing the same search algorithm used for vehicular route searches.
According to another aspect of the present invention, when configuring a service route of a public transportation service using links and nodes, the node information includes a node denoting the location of a parking lot near a boarding site of the public transportation service, and the link information includes a link connecting the nodes denoting the locations of the boarding site and the parking lot. When the public transportation service is railway, the node information includes nodes denoting the locations of the railway stations, and the link information includes links connecting between those nodes denoting the station locations. The node information may further include a node denoting the location of a railway station and a node denoting the location of a parking lot near the station, while the link information may further include a link connecting between those nodes. When a plurality of railway lines exist, such node information and link information may beconfigured for each railway line. Furthermore, the node information may include a node denoting a road near a station in addition to a node denoting the location of the station, and the link information may include a link connecting those nodes.
In a further aspect of the present invention, the memory means for storing public transportation service routes uses the link information and the node information to further store data related to walking routes as additional link and node information. The calculation means can calculate a route on foot based on the link information and the node information related to walking routes.
In another aspect of the present invention, the route guiding apparatus comprises a location detection means for detecting the current location, a memory means for storing map data, a traveling mode detection means for detecting the current traveling mode, and a correction means for correcting the detected current location by correlating the map data in accordance with the traveling mode. To determine the current location with a high precision, map matching (MM) processing is effective. In MM processing, the current location detected via GPS or other means is correlated with the map data and matched to an appropriate location within the map data. When traveling by vehicle, the current location can be accurately determined by referring to the road closest to the detected current location or the most appropriate point on the road (such as an intersection). However, such MM technique cannot be directly implemented when traveling via a public transportation route because the traveling mode is not by vehicle. Whereas the conventional MM technique can be used to correct the current location when traveling by vehicle, the railway service schedule is used to correct the current location when traveling via railway. When traveling on foot, MM may not be executed. In this way, the current location can be corrected using different processing algorithms in accordance with each traveling mode, allowing precise detection of the current location even when traveling using public transportation.
Still further, the present invention provides a computer-readable medium on which is recorded a program for searching a route leading to a destination. By executing the program, a computer performs the steps of (a) searching for a route using vehicle only to reach the destination, (b) calculating the cost of the route using vehicle only, (c) searching for a route using public transportation, (d) calculating the cost of the route using public transportation, and (e) outputting the route using public transportation when the cost of the route using public transportation is smaller by a predetermined value or more compared to the cost of the route using vehicle only. The medium may include any arbitrary medium that can store information electromagnetically, optically, or chemically, such as a CD-ROM, DVD, FD, hard-disk, and semiconductor memory. The program stored in the medium is installed in the computer and executed by the processor of the computer.